This invention relates to methods for delivering and deploying modular sections of an endovascular stent/graft for assembly thereof within the vasculature of a patient and specifically to a system for accomplishing the same.
It is well established that various fluid conducting body or corporeal lumens, such as veins and arteries, may deteriorate or suffer trauma so that repair is necessary. For example, various types of aneurysms or other deteriorative diseases may effect the ability of the lumen to conduct fluids and, in turn, may be life threatening. In some cases, the damage to the lumen is repairable only with the use of prosthesis such as an artificial vessel or graft.
For repair of vital lumens such as the aorta, surgical repair is significantly life threatening or subject to significant morbidity. Surgical techniques known in the art involve major surgery in which a graft resembling the natural vessel is spliced into the diseased or obstructed section of the natural vessel. Known procedures include surgically removing the damaged or diseased portion of the vessel and inserting an artificial or donor graft portion inserted and stitched to the ends of the vessel which were created by the removal of the diseased portion. More recently, devices have been developed for treating diseased vasculature through intraluminal repair. Rather than removing the diseased portion of the vasculature, the art has taught bypassing the diseased portion with a prosthesis and implanting the prosthesis within the vasculature. An intra arterial prosthesis of this type has two components: a flexible conduit, the graft, and the expandable framework, the stent (or stents). Such a prosthesis is called an endovascular graft.
It has been found that many abdominal aortic aneurysms extend to the aortic bifurcation. Accordingly, a majority of cases of endovascular aneurysm repair employ a graft having a bifurcated shape with a trunk portion and two limbs, each limb extending into separate branches of vasculature. Currently available bifurcated endovascular grafts fall into two categories. One category of grafts are those in which a preformed graft is inserted whole into the arterial system and manipulated into position about the area to be treated. This is a unibody graft. The other category of endovascular grafts are those in which a graft is assembled in-situ from two or more endovascular graft components. This latter endovascular graft is referred to as a modular endovascular graft. Because a modular endovascular graft facilitates greater versatility of matching individual components to the dimensions of the patient's anatomy, the art has taught the use of modular endovascular grafts in order to minimize difficulties encountered with insertion of the devices into vasculature and sizing to the patient's vasculature.
Although the use of modular endovascular grafts minimize some of the difficulties, there are still drawbacks associated with the current methods. Drawbacks with current methods can be categorized in three ways; drawbacks associated with delivery and deployment of the individual endovascular graft components, drawbacks associated with the main body portion, and drawbacks associated with securing the limb portions to the main body portion.
The drawbacks of current methods of delivery and deployment of endovascular graft components include redundant components for delivery, delivery of both a graft and its securing stent as a single entity, and at least minor surgery in order to gain access to the vasculature of the patient. Current methods for delivering the individual components of a modular endovascular graft to the treatment site require the use of a separate delivery catheter for each component and exchange of the delivery catheters through an introducer sheath after each component has been deployed. There are a number of disadvantages to this method. Since each delivery catheter has to be smaller than the introducer sheath, this limits the design of the implant, makes packing the implant into the delivery system more difficult, and increases the force required to deploy the implant. The use of multiple delivery catheters increases production costs and decreases reliability due to the multiplicity of catheter parts required. The process of removing one delivery system and replacing it with another may require coordination between two operators to ensure that guidewire access is maintained, a longer guidewire, additional procedure time, a large amount of physical space, and additional trauma to the insertion and delivery sites.
Furthermore, the known methods for delivering grafts to the required location within a patient's vascular system also require that an attachment system be delivered simultaneously with the graft, axially overlapping the graft and located either on the interior or the exterior of the graft's lumen, so that upon deployment of the graft the attachment system is expanded to attach the graft to the vascular wall. The attachment system is typically connected to the graft before implantation in the patient by means such as stitching. As a consequence, the outer diameter of the delivery capsule or sheath containing the compressed graft is increased by the presence of the compressed attachment system. Complications may be encountered in maneuvering the compressed graft and its delivery system around the bends and branches of the patient's vascular system. It will be appreciated that the greater the outer dimension of the capsule containing the compressed graft to be delivered, the more inflexible it will be, making delivery to the final destination more difficult and perhaps even impossible in some patients.
Moreover, in the majority of cases, the patient must be subject to surgery in which the appropriate vessel is surgically exposed and opened by incision to allow entry of the graft. Significantly, it is this surgical procedure on the vessel which gives rise to the most serious complications such as infection, patient discomfort, and necrosis of the vessel itself. However, if the outside dimension of the delivery capsule were sufficiently small, it might be possible, depending on the size and condition of the patient, to insert the capsule into the patient's vessel by applying sufficient force to the skin and artery of the patient with a sharpened end of the graft's delivery capsule, similar to the commonly known method of inserting a needle directly into the vein or artery of a patient.
The drawbacks of current embodiments of the main body component of a modular endovascular graft include a relatively large delivery profile due to the aforementioned graft and supporting stent as a single entity as well as additional stents within the separate branches of a bifurcated main body portion, difficulty in catheterizing the connection site of the first endovascular graft component prior to introduction of the second endovascular graft component, and a lack of adequate healthy tissue near the aneurysm for anchoring the graft to the aortic wall. Although the prior art has taught that the larger delivery profile of a combined graft and supporting stent can be minimized by providing separate support stents for the trunk and limb support branches of the main body component rather than a single support stent for the entire main graft component, separate support stents for the limb support branches are conventionally located at the same axial level. This results in a larger delivery profile since the support stents, when collapsed for delivery, lie on top of each other.
Furthermore, because of the restricted geometry of the vasculature and the small diameter of the limb supporting branch of the main body component, it can be difficult to insert one element of a modular endovascular graft into another. The instrumentation required to insert catheters and deploy the limb components of a modular endovascular graft inside the main graft limb support sections can dislodge mural thrombus in the AAA. The dislodged mural thrombus is carried in the blood flow through the femoral arteries to small distal arteries causing blockage and tissue necrosis.
Moreover, a lack of healthy tissue near the aneurysm being treated provides difficulty with adequately anchoring the main body portion of a modular endovascular graft. If the aneurysm is too close to the renal arteries there may be a lack of healthy tissue to adequately anchor the neck of the main graft portion without interfering with blood flow in the renal arteries. If the aneurysm extends too close to the bifurcation of the vasculature, there may be a lack of healthy tissue to adequately anchor the limb support branches of the main body component. Anchoring the limb support branches of the main body component in the iliac arteries requires a larger main body component and additional effort and delivery hardware. Allowing the limb support branches of the main body component to float freely in the aneurysm presents other difficulties with deploying the limb components of the modular endovascular graft within the main body component.
With regard to the method of delivery and deployment of endovascular graft components, there therefore exists a need for a endovascular graft delivery system that limits the amount of redundancy of delivery components required, can be easily operated by a single technician without decreased reliability or additional risk to the patient, facilitates a reduced outside dimension of the capsule or sheath containing a compressed graft component to be delivered to the patient's vascular system, and minimizes the need for surgery in order to gain entry to the patient's vasculature.
The devices and methods of the present invention addresses these and other needs.